Aim: To prepare a1,3-diphenyl pyrazole from diphenyl hydrazone vicinal diol.
Chemicals Required: 1-benzyledene-2-phenyl hydrazine, ethylene glycol, Ferric Chloride, Tert-butyl hydroperoxide, Acetyl acetone, Sodium chloride, Ethyl acetate, Sodium sulphate.
Apparatus:
- Conical flask
- Beaker
- Measuring cylinder
Principle: 1,3 substituted pyrazole is prepared by cyclization of diarylhydrazone and vicinal diol in presence of ferric chloride and tert-butylhydroperoxide(TBHP) which is also called regioselective synthesis of substituted pyrazole.
Reaction :
About 4.55g of 1-benzyledene-2- phenyl hydrazine is dissolved in the solution of 25ml of vicinal diol and ferric chloride(5mol%). Then another solution of tert-butyl hydroperoxide(5.3g) in 25ml of acetyl acetone is added into it. The mix solution is kept maintaining at a temperature range of 90-100°C. The mix solution is left to reach room temperature and stirred for 6hrs. Then the content is poured into water and extracted with ethyl acetate 3times. The combined organic solution is washed with water, then with a saturated solution of sodium chloride, passed through sodium sulphate and evaporated under vacuum.
Uses: Can be used as antibacterial and antiviral agent.
Calculation:
Molecular formula of 1-benzyledene-2-phenyl hydarzine = C13H12N2
Molecular Formula of 1,3-diphenyl pyrazole = C15H12N2
Molecular Weight of 1-benzyledene-2-phenyl hydarzine =196g/mol
Molecular Weight of 1,3-diphenyl pyrazole = 220g/mol
196g/mol 1-benzyledene-2-phenyl hydarzine yields 1,3-diphenyl pyrazole =220g
4.55g 1-benzyledene-2-phenyl hydarzine shall yields 1,3-diphenyl pyrazole= (220/196)x 4.55 = 5.1g
Therefore, Theoretical yields of 1,3-diphenyl pyrazole = 3.15g
If reported practical yield =3.15g
Then, percentage practical yield= (Practical yield/ Theoritical yeild) x 100
=(3.15/5.1)x100 = 61.76%
Report : The percentage yield of 1,3-diphenyl pyrazole is 61.76?% with m.p. 185°C
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